The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
A powertrain includes a torque generative device, providing torque to a rotating member. A hybrid powertrain utilizes at least two torque generative devices, for example an internal combustion engine and one or more electric machines. A hybrid transmission is employed and configured to selectively receive and transmit torque through the various gear members and change gear states to establish a relationship between a rotational input to the transmission and a rotational output of the transmission.
It is known to employ diesel combustion engines due to their ability to produce desirable torque utilizing air-fuel ratios that are lean of stoichiometry. While the lean air-fuel ratios provide increased fuel economy compared to gasoline engines, emissions efficiency is reduced due to increased levels of NOx and hydrocarbons output from the diesel engine. Accordingly, if the diesel engine is optimized to obtain the greatest fuel efficiency, increased levels of emissions may result. Additionally, fuel economy can be reduced indirectly if aftertreatment systems require frequent cleaning and regeneration. However, aftertreatment devices of exhaust aftertreatment systems that are required to purify regulated constituents within an exhaust gas feedstream need to be periodically cleaned and must be operated at or above a threshold temperature to ensure efficient operation.
It is known to increase the exhaust gas feedstream temperature to carryout required cleaning and/or heating events of aftertreatment devices by increasing the load and/or operating the engine rich of stoichiometry. Sub-optimization of the diesel engine is often required to maintain desired axle torques in response to increased injected fuel masses utilized to increase the exhaust gas feedstream temperature. For instance, sub-optimization can include retarding the combustion phasing from an ideal combustion phasing, and/or operating auxiliary components of the vehicle such that an alternator is depleted to take on extra torque provided by the engine. Sub-optimizing the engine can reduce fuel economy and drivability of the vehicle.